Other scientists have had similar findings, but this study conducted in Spain is the first major clinical trial. Previous research mostly showed that people living in Mediterranean countries had low risk of heart disease. The studies did not account for other factors that could have influenced health.

The latest study divided people with high risk of heart disease into three groups. One-third adopted a Mediterranean-style diet and were given one liter a week of extra virgin olive oil. Another third adopted a Mediterranean-style diet and were given an ounce of nuts eacth day. The third group adopted a low-fat diet.

The trial was stopped early, after five years, because the evidence was so strong that the Mediterranean diet benefited cardiovascular health.